Re: [Intel-gfx] [PATCH 1/3] drm/atomic-helper: reset vblank on crtc reset

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Wed, Jun 3, 2020 at 2:19 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Daniel,
>
> Thank you for the patch.
>
> May I remind you about the -v option to git-format-patch ? :-) Seriously
> speaking, it really helps review.
>
> On Tue, Jun 02, 2020 at 11:51:38AM +0200, Daniel Vetter wrote:
> > Only when vblanks are supported ofc.
> >
> > Some drivers do this already, but most unfortunately missed it. This
> > opens up bugs after driver load, before the crtc is enabled for the
> > first time. syzbot spotted this when loading vkms as a secondary
> > output. Given how many drivers are buggy it's best to solve this once
> > and for all in shared helper code.
> >
> > Aside from moving the few existing calls to drm_crtc_vblank_reset into
> > helpers (i915 doesn't use helpers, so keeps its own) I think the
> > regression risk is minimal: atomic helpers already rely on drivers
> > calling drm_crtc_vblank_on/off correctly in their hooks when they
> > support vblanks. And driver that's failing to handle vblanks after
> > this is missing those calls already, and vblanks could only work by
> > accident when enabling a CRTC for the first time right after boot.
> >
> > Big thanks to Tetsuo for helping track down what's going wrong here.
> >
> > There's only a few drivers which already had the necessary call and
> > needed some updating:
> > - komeda, atmel and tidss also needed to be changed to call
> >   __drm_atomic_helper_crtc_reset() intead of open coding it
> > - tegra and msm even had it in the same place already, just code
> >   motion, and malidp already uses __drm_atomic_helper_crtc_reset().
> >
> > Only call left is in i915, which doesn't use drm_mode_config_reset,
> > but has its own fastboot infrastructure. So that's the only case where
> > we actually want this in the driver still.
> >
> > I've also reviewed all other drivers which set up vblank support with
> > drm_vblank_init. After the previous patch fixing mxsfb all atomic
> > drivers do call drm_crtc_vblank_on/off as they should, the remaining
> > drivers are either legacy kms or legacy dri1 drivers, so not affected
> > by this change to atomic helpers.
> >
> > v2: Use the drm_dev_has_vblank() helper.
> >
> > v3: Laurent pointed out that omap and rcar-du used drm_crtc_vblank_off
> > instead of drm_crtc_vblank_reset. Adjust them too.
> >
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> > Acked-by: Liviu Dudau <liviu.dudau@arm.com>
> > Acked-by: Thierry Reding <treding@nvidia.com>
> > Link: https://syzkaller.appspot.com/bug?id=0ba17d70d062b2595e1f061231474800f076c7cb
> > Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > Reported-by: syzbot+0871b14ca2e2fb64f6e3@syzkaller.appspotmail.com
> > Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > Cc: "James (Qian) Wang" <james.qian.wang@arm.com>
> > Cc: Liviu Dudau <liviu.dudau@arm.com>
> > Cc: Mihail Atanassov <mihail.atanassov@arm.com>
> > Cc: Brian Starkey <brian.starkey@arm.com>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Boris Brezillon <bbrezillon@kernel.org>
> > Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
> > Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> > Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Cc: David Airlie <airlied@linux.ie>
> > Cc: Daniel Vetter <daniel@ffwll.ch>
> > Cc: Thierry Reding <thierry.reding@gmail.com>
> > Cc: Jonathan Hunter <jonathanh@nvidia.com>
> > Cc: Jyri Sarha <jsarha@ti.com>
> > Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> > Cc: Rob Clark <robdclark@gmail.com>
> > Cc: Sean Paul <seanpaul@chromium.org>
> > Cc: Brian Masney <masneyb@onstation.org>
> > Cc: Emil Velikov <emil.velikov@collabora.com>
> > Cc: zhengbin <zhengbin13@huawei.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: linux-tegra@vger.kernel.org
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 7 ++-----
> >  drivers/gpu/drm/arm/malidp_drv.c                 | 1 -
> >  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c   | 7 ++-----
> >  drivers/gpu/drm/drm_atomic_state_helper.c        | 4 ++++
> >  drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c        | 2 --
> >  drivers/gpu/drm/omapdrm/omap_drv.c               | 3 ---
> >  drivers/gpu/drm/rcar-du/rcar_du_crtc.c           | 3 ---
> >  drivers/gpu/drm/tegra/dc.c                       | 1 -
> >  drivers/gpu/drm/tidss/tidss_crtc.c               | 3 +--
> >  drivers/gpu/drm/tidss/tidss_kms.c                | 4 ----
> >  10 files changed, 9 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> > index 56bd938961ee..f33418d6e1a0 100644
> > --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> > +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> > @@ -492,10 +492,8 @@ static void komeda_crtc_reset(struct drm_crtc *crtc)
> >       crtc->state = NULL;
> >
> >       state = kzalloc(sizeof(*state), GFP_KERNEL);
> > -     if (state) {
> > -             crtc->state = &state->base;
> > -             crtc->state->crtc = crtc;
> > -     }
> > +     if (state)
> > +             __drm_atomic_helper_crtc_reset(crtc, &state->base);
> >  }
> >
> >  static struct drm_crtc_state *
> > @@ -616,7 +614,6 @@ static int komeda_crtc_add(struct komeda_kms_dev *kms,
> >               return err;
> >
> >       drm_crtc_helper_add(crtc, &komeda_crtc_helper_funcs);
> > -     drm_crtc_vblank_reset(crtc);
> >
> >       crtc->port = kcrtc->master->of_output_port;
> >
> > diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
> > index c2507b7d8512..02904392e370 100644
> > --- a/drivers/gpu/drm/arm/malidp_drv.c
> > +++ b/drivers/gpu/drm/arm/malidp_drv.c
> > @@ -870,7 +870,6 @@ static int malidp_bind(struct device *dev)
> >       drm->irq_enabled = true;
> >
> >       ret = drm_vblank_init(drm, drm->mode_config.num_crtc);
> > -     drm_crtc_vblank_reset(&malidp->crtc);
> >       if (ret < 0) {
> >               DRM_ERROR("failed to initialise vblank\n");
> >               goto vblank_fail;
> > diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> > index 10985134ce0b..ce246b96330b 100644
> > --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> > +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> > @@ -411,10 +411,8 @@ static void atmel_hlcdc_crtc_reset(struct drm_crtc *crtc)
> >       }
> >
> >       state = kzalloc(sizeof(*state), GFP_KERNEL);
> > -     if (state) {
> > -             crtc->state = &state->base;
> > -             crtc->state->crtc = crtc;
> > -     }
> > +     if (state)
> > +             __drm_atomic_helper_crtc_reset(crtc, &state->base);
> >  }
> >
> >  static struct drm_crtc_state *
> > @@ -528,7 +526,6 @@ int atmel_hlcdc_crtc_create(struct drm_device *dev)
> >       }
> >
> >       drm_crtc_helper_add(&crtc->base, &lcdc_crtc_helper_funcs);
> > -     drm_crtc_vblank_reset(&crtc->base);
> >
> >       drm_mode_crtc_set_gamma_size(&crtc->base, ATMEL_HLCDC_CLUT_SIZE);
> >       drm_crtc_enable_color_mgmt(&crtc->base, 0, false,
> > diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> > index 8fce6a115dfe..9ad74045158e 100644
> > --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> > @@ -32,6 +32,7 @@
> >  #include <drm/drm_device.h>
> >  #include <drm/drm_plane.h>
> >  #include <drm/drm_print.h>
> > +#include <drm/drm_vblank.h>
> >  #include <drm/drm_writeback.h>
> >
> >  #include <linux/slab.h>
> > @@ -93,6 +94,9 @@ __drm_atomic_helper_crtc_reset(struct drm_crtc *crtc,
> >       if (crtc_state)
> >               __drm_atomic_helper_crtc_state_reset(crtc_state, crtc);
> >
> > +     if (drm_dev_has_vblank(crtc->dev))
> > +             drm_crtc_vblank_reset(crtc);
> > +
> >       crtc->state = crtc_state;
> >  }
> >  EXPORT_SYMBOL(__drm_atomic_helper_crtc_reset);
> > diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> > index ca3368c828d0..9606185c284b 100644
> > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> > @@ -1117,8 +1117,6 @@ static void mdp5_crtc_reset(struct drm_crtc *crtc)
> >               mdp5_crtc_destroy_state(crtc, crtc->state);
> >
> >       __drm_atomic_helper_crtc_reset(crtc, &mdp5_cstate->base);
> > -
> > -     drm_crtc_vblank_reset(crtc);
> >  }
> >
> >  static const struct drm_crtc_funcs mdp5_crtc_funcs = {
> > diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> > index 242d28281784..7a7066cded79 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> > +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> > @@ -642,9 +642,6 @@ static int omapdrm_init(struct omap_drm_private *priv, struct device *dev)
> >               goto err_cleanup_modeset;
> >       }
> >
> > -     for (i = 0; i < priv->num_pipes; i++)
> > -             drm_crtc_vblank_off(priv->pipes[i].crtc);
> > -
> >       omap_fbdev_init(ddev);
> >
> >       drm_kms_helper_poll_init(ddev);
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> > index d73e88ddecd0..e2959e32fd19 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> > @@ -1271,9 +1271,6 @@ int rcar_du_crtc_create(struct rcar_du_group *rgrp, unsigned int swindex,
> >
> >       drm_crtc_helper_add(crtc, &crtc_helper_funcs);
> >
> > -     /* Start with vertical blanking interrupt reporting disabled. */
> > -     drm_crtc_vblank_off(crtc);
> > -
>
> I'm sure I've added this code for a good reason, I would have sworn that
> vblank would be either broken or would complain very loudly without this
> call. I've however tested this patch, and haven't noticed any
> regression. Has something changed since I've added the call to
> drm_crtc_vblank_off() in the rcar-du driver ? It can't be
> __drm_atomic_helper_crtc_reset() handling it, as the rcar-du driver has
> a custom CRTC reset handler that doesn't call
> __drm_atomic_helper_crtc_reset(). If it works without calling
> drm_crtc_vblank_off() or drm_crtc_vblank_reset(), what's the purpose of
> drm_crtc_vblank_reset() ?
>
> /me is very puzzled

Uh yeah this breaks stuff, I forgot to review the two drivers I've
changed to make sure they're using the __drm_atomic_helper_crtc_reset
function. Like they should. I'll respin.
-Daniel

> >       /* Register the interrupt handler. */
> >       if (rcar_du_has(rcdu, RCAR_DU_FEATURE_CRTC_IRQ_CLOCK)) {
> >               /* The IRQ's are associated with the CRTC (sw)index. */
> > diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
> > index 83f31c6e891c..9b308b572eac 100644
> > --- a/drivers/gpu/drm/tegra/dc.c
> > +++ b/drivers/gpu/drm/tegra/dc.c
> > @@ -1168,7 +1168,6 @@ static void tegra_crtc_reset(struct drm_crtc *crtc)
> >               tegra_crtc_atomic_destroy_state(crtc, crtc->state);
> >
> >       __drm_atomic_helper_crtc_reset(crtc, &state->base);
> > -     drm_crtc_vblank_reset(crtc);
> >  }
> >
> >  static struct drm_crtc_state *
> > diff --git a/drivers/gpu/drm/tidss/tidss_crtc.c b/drivers/gpu/drm/tidss/tidss_crtc.c
> > index 89a226912de8..4d01c4af61cd 100644
> > --- a/drivers/gpu/drm/tidss/tidss_crtc.c
> > +++ b/drivers/gpu/drm/tidss/tidss_crtc.c
> > @@ -352,8 +352,7 @@ static void tidss_crtc_reset(struct drm_crtc *crtc)
> >               return;
> >       }
> >
> > -     crtc->state = &tcrtc->base;
> > -     crtc->state->crtc = crtc;
> > +     __drm_atomic_helper_crtc_reset(crtc, &tcrtc->base);
> >  }
> >
> >  static struct drm_crtc_state *tidss_crtc_duplicate_state(struct drm_crtc *crtc)
> > diff --git a/drivers/gpu/drm/tidss/tidss_kms.c b/drivers/gpu/drm/tidss/tidss_kms.c
> > index 4b99e9fa84a5..e6ab59eed259 100644
> > --- a/drivers/gpu/drm/tidss/tidss_kms.c
> > +++ b/drivers/gpu/drm/tidss/tidss_kms.c
> > @@ -278,10 +278,6 @@ int tidss_modeset_init(struct tidss_device *tidss)
> >       if (ret)
> >               return ret;
> >
> > -     /* Start with vertical blanking interrupt reporting disabled. */
> > -     for (i = 0; i < tidss->num_crtcs; ++i)
> > -             drm_crtc_vblank_reset(tidss->crtcs[i]);
> > -
> >       drm_mode_config_reset(ddev);
> >
> >       dev_dbg(tidss->dev, "%s done\n", __func__);
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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